This invention relates to a device which permits simultaneous analysis of a plurality of radioactively labeled discrete reaction or isolation zones such as in a plurality of filters. More particularly, this invention relates to a device for transferring a plurality of radioactively labeled samples to an apparatus for analyzing the samples.
Test plates for in vitro analysis which contain a multiplicity of individual wells or reaction chambers are commonly known laboratory tools. Such devices have been employed for a wide variety of purposes and assays as exemplified by U.S. Pat. Nos. 3,694,464; 4,304,865; 4,276,048; 4,427,415; 4,526,690 and Re 30,562. Microporous membrane filters and filtration devices containing such microporous membranes have been especially useful with many of the recently developed cell and tissue culture techniques and assays, particularly those in the field of virology, cell biology, phamacology, immunology and molecular biology, wherein the material of interest is retained by the filter. Typically, a ninety-six well filtration plate is used to conduct multiple assays simultaneously. Often the material of interest is retained on the filter. However, if an analytical instrument used for sample quantification cannot detect samples on the filters situated directly in the plate wells, the filters must be removed from the wells. This is particularly true when using a weak radiation emitter such as tritium because emissions travel such a short distance from their source and in typical detectors, the well height exceeds the emission distance.
It also has been proposed to utilize a die-punch having a flat face which is inserted into the well and through the filter paper bearing the retentate in order to direct the filter paper and retentate from the well into a vial for subsequent testing. This system has major problems. Scintillation fluid is a hazard which generates a large volume of waste which is costly to dispose of. Any cutting or punching tools can cross contaminate samples. Therefore each sample must have its own punch which generates more waste. In addition, many times only a portion of the filter paper circumference is sheared and the filter disc remains attached to the well. Also, the flat face of the punch tends to remove some of the retentate from the filter paper so that the subsequent testing is inaccurate. An alternative system utilizes a hollow tube as a punch to minimize the contact face of the punch and reduce the amount of sample accidently transferred to the punch. In another system, the filter is scored about its circumference in order to facilitate subsequent punching. This system is undesirable since accidental rupturing of the filter along the scoring can occur.
It has been proposed in U.S. Pat. No. 4,639,601 and U.K. Patent Application 2,168,526A to provide an analytical apparatus for counting radioactive emissions from a plurality of samples. The samples are deposited on a sheet such as from a chromatographic or electrophoretic separation step to produce a radiochromatogram or an electrophoretogram. The apparatus utilizes a resolution plate to isolate the samples from each other as well as a reusable metal plate which permits an appropriate level of electrostatic discharge. These plates are undesirable since they are heavy and cumbersome and are prone to contamination which must be removed through extensive washing prior to analyzing the next successive set of samples. In addition, this apparatus is not capable of analyzing samples labeled with tritium and the reusable metal plate produces a path between the sample and the radioactivity detector which is too long to permit accurate emission measurement.
Accordingly, it would be desirable to provide a means for removing retentate and filter from a multi-well filtration plate which assures that the filter will be completely removed from the well without the loss of a portion of the retentate for purposes of subsequent testing. It would be desirable to provide such a means which maintains sample array spacing to prevent sample cross-talk and which can be easily handled for presentation into an available analytical instrument. Furthermore, it would be desirable to provide such a means onto a surface so that it can be utilized directly in an analytical apparatus while eliminating contamination associated with a reusable metal plate. In addition, it would be desirable to provide such a means which permits record keeping on a disposable unit.